Apparatus for preventing circumferential overspeeding of grinding wheels

ABSTRACT

Apparatus for preventing circumferential overspeeding of grinding wheel comprises spindle with wheel connected thereto and motor assembly connected to spindle for rotating wheel. Motor assembly includes small diameter pulley for rotating large diameter grinding wheel. Assembly also includes alternate large diameter pulley for rotating worn substantially less than large diameter grinding wheel. Movable linkage is located between periphery of grinding wheel and periphery of pulley connected to rotate wheel. Linkage prevents replacement of worn wheel with new large diameter wheel when large diameter pulley is connected to rotate wheel since large diameter pulley operates to position movable linkage at location which is to be occupied by new large diameter wheel.

United States Patent Kikuchi et a1.

[15] 3,656,262 1 Apr. 18, 1972 [54] APPARATUS FOR PREVENTING CIRCUMFERENTIAL OVERSPEEDING 2,471,561 5/1949 Fielding ..51/269 Primary Examiner-Donald G. Kelly Attorney-Connolly and lint:

[ 57] ABSTRACT Apparatus for preventing circumferential overspeeding of grinding wheel comprises spindle with wheel connected thereto and motor assembly connected to spindle for rotating wheel. Motor assembly includes small diameter pulley for rotating large diameter grinding wheel. Assembly also includes alternate large diameter pulley for rotating worn substantially less than large diameter grinding wheel. Movable linkage is located between periphery of grinding wheel and periphery of pulley connected to rotate wheel. Linkage prevents replacement of worn wheel with new large diameter wheel when large diameter pulley is connected to rotate wheel since large diameter pulley operates to position movable linkage at location which is to be occupied by new large diameter wheel.

3 Claims, 3 Drawing Figures PATENTEDAPR 1 1912 SHEET 1 [IF 2 the low-speed small diameter motor APPARATUS FOR PREVENTING CIRCUMFERENTIAL OVERSPEEDING OF GRINDING WHEELS BACKGROUND OF THE INVENTION Thepresent invention relates to an apparatus for preventing circumferential overspeeding of a grinding wheel.

In the conventional grinding of a work piece on the periphery of a grinding wheel, the wheel driving mechanism usually comprises a motor pulley, a grinding wheel spindle pulley, and belts interconnecting these pulleys for transmitting motion from the motor to the grinding wheel spindle. Thus, the rotary motion of the motor is ultimately transmitted to the grinding wheel for rotating it. The rotary speed of the grinding wheel spindle is constant for each given ratio of diameters of the motor and spindle pulleys. However, as the outer volume of the grinding wheel is reduced with progressive wear, the cirplished when the grinding wheel is approximately half worn.

After complete wearing away of the grinding wheel to its minimum diameter, the worn out wheel is removed and replaced with a new large diameter wheel. The operator often forgets to exchange the high-speed large diameter pulley on the motor shaft for the low-speed small diameter pulley. Accordingly, when the large diameter grinding wheel is mounted and the grinding machine starts, the circumferential speed of the wheel is excessively high. This may cause the wheel to break as well as cause unnecessary wear and tear on the equipment. Various measures for preventing circumferential overspeeding of the grinding wheel have been devised, but even in a universal grinding machine designed when the positions of grinding wheel, grinding wheel guard and motor pulleys exchange between right and left, it has been difficult to effect prevention of circumstances which cause circumferential overspeeding of the grinding wheel. Thus, development of a grinding wheel system which is capable of safe and rapid operation has long been in demand.

SUMMARY OF THE INVENTION It is the general object of the present invention to provide an apparatus that eliminates the hazard of excessive peripheral grinding wheel speed which hazard often causes the premature destruction of grinding wheels as well as significant decreases in work efficiency.

Another object of the present invention is to provide a mechanism which prevents a large diameter grinding wheel from being positioned upon a grinding machine when the power transmission to that wheel is such that it will cause the wheel to rotate at an excessive peripheral speed.

In accordance with the present invention an apparatus is provided for preventing circumferential overspeeding of a grinding wheel. The apparatus comprises a spindle with a grinding wheel connected thereto and a motivator connected to the spindle for rotating the grinding wheel. The motivator includes a small diameter pulley which is connected to rotate a large diameter grinding wheel together with an alternate large diameter pulley which is connected to rotate a worn substantially less than large diameter grinding wheel. The alternate pulleys enable somewhat constant peripheral grinding wheel speed. A movable linkage is connected between the periphery of the grinding wheel and the periphery of the motor pulley connected to rotate the wheel. The linkage has a first position in which it is located directly adjacent the periphery of the small diameter pulley and also directly adjacent the periphery of a large diameter grinding wheel. The linkage has a second position in which it is located directly adjacent the periphery of the alternate large diameter pulley and also directly adjacent the periphery of a worn substantially less than a large diameter grinding wheel. The second position of the linkage prevents replacement of a completely worn grinding wheel with a new large diameter grinding wheel until the linkage is shifted to the first position. The large diameter alternate pulley prevents shifting of the linkage to the first position until the alternate pulley is replaced with the small diameter pulley. Thus, a new large diameter wheel may only be positioned on the spindle after the large diameter pulley is removed whereby circumferential overspeeding of the new large diameter wheel is prevented.

BRIEF DESCRIPTION OF THE DRAWING Novel features and advantages of the present invention in addition to those mentioned above will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing wherein:

FIG. 1 is a side elevational viewof an apparatus according to the present invention;

FIG. 2 is a top plan view of the apparatus shown in FIG. 1; and

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity to the drawing, FIGS. 1 and 2 illustrate a grinding mechanism including a grinding wheel spindle 2.rotatably mounted upon a grinding wheel head 1. A grinding wheel 3 is fixed at one end of the grinding wheel spindle 2 while a pulley 4 is secured to the other side of the spin dle. A grinding wheel guard 5 attached to the grinding wheel head 1 substantially surrounds the grinding wheel 3.

As shown best in FIG. 1, the grinding wheel guard 5 includes a side plate 5a having an arcua'tely formed rejecting pin slot 8 formed therein. As explained more fully below, the arcuate slot 8 in the side plate 521 is arranged to receive a large diameter grinding wheel rejecting pin 21. A front cover 6 is bolted with fasteners 7 to the upper edge of the grinding wheel guard 5 for the purpose of protecting the grinding wheel 3. A motor 9 is movably mounted at the rear of the grinding wheel head 1. The motor has an axis which is parallel to the grinding wheel spindle 2. Pulleys 18, 19 are provided for attachment to the motor axis and V-belts are trained over the pulleys mounted on the motor axis and the spindle for transmitting power from motor 9 to the spindle when the motor is activated. Tensioning devices may be provided for the purpose of tensioning the V-belts. Specifically, the motor 9 is fixed to a motor base 10 slidably mounted on a guide surface la formed on the grinding wheel head 1 in transverse direction to the grinding wheel spindle axis. A hand wheel 11 penetrates a screw support 13 fitted to the grinding wheel 1 and the wheel 11 is attached to a feed screw 12. The feed screw 12 mates with the motor base 10 and serves to shift the motor base along the guide surface la when the hand wheel is manipulated. With the screw support 13 located between a pair of fixed abutments comprising an end face 11a of the hand wheel 11 and a step 12a of the screw 12, axial displacement of the screw 12 during rotation thereof is prevented.

It is possible to arrange the grinding wheel 3 and pulley 4 exchanged between position right and left whereby it is possible to reverse the positions of the grinding wheel guard 5 and the motor 9 which is fitted to the grinding wheel head 1. Side plates 5a, 5b of the grinding wheel guard 5 are exchanged in fitting position respectively and the side plate 5a provided with the rejecting pin slot 8 is always located on the inside.

The device or mechanism for preventing the circumferential overspeeding of the grinding wheel 3 is described below in conjunction with the structure explained above. Approximately midway between the grinding wheel 3 and the motor 9, a linkage is provided on the grinding wheel head 1 for preventing circumferential overspeeding of the grinding wheel. The linkage includes a link shaft 14 parallel to the grinding wheel spindle 2. As shown best in FIG. 3, the shaft 14 is held by supports 15, secured with bolts 16, 16 to the side faces of the grinding wheel head 1. The supports 15, 15 have a plurality of adjustment screws 17, 17 for adjusting the spacing between the supports. The end portions or tips of the adjustment screws 17, 17 engage the side faces of the grinding wheel head 1.

The linkage also includes safety arms 20, mounted upon the axis 14 for swinging toward and away from the pulleys l8, 19. In other words, the arms 20 swing toward and away from the axis of rotation of the motor 9. Fasteners 26, 26 function to secure the safety arms 20, 20 to the shaft 14. Solidly formed high-speed pulley rejecting means 20a, 20a are provided at the outer ends of the safety arms 20. Also, large diameter grinding wheel rejecting pins 21, 21 are fixed to levers 22, 22 pivotally attached to the safety arms 20, 20 at the outer ends thereof by pivots 23, 23. The axial displacements of the safety arms 20 and the levers 22 are restricted by bolts 24, 24. Moreover, downward swing motion of the levers 22 is limited by a projecting part 22' which engages the arms 20 to prevent contact of the levers 22 with the V-belts 25.

When the diameter of the grinding wheel is reduced from diameter a to diameter b (FIG. 1), the large diameter grinding wheel rejecting pin 21 on the side of the machine where the grinding wheel 3 is located is held at a first position in the arcuate slot 8 which position is identified by reference numeral 8a. When this rejecting pin 21 is shifted to its second position illustrated by reference numeral 8b the rejecting pin 21 juts out into the space normally occupied by the outermost material of a new large diameter grinding wheel. The rejecting pin is urged to the position 812 by the lever 22 to which it is attached, the lever being urged toward the axis of rotation of the grind ing wheel by the arms 20 or more specifically'the rejecting means 20a solidly attached to the ends of the arms 20. The arms 20 are urged to the right, as viewed in FIG. 1, when it is desired to change from a small diameter pulley 18 to a larger diameter pulley 19. As explained above the purpose of this change is to increase the peripheral speed of a worn grinding wheel having a somewhat lower peripheral speed due to the decrease of diameter of the grinding wheel.

When the grinding wheel 3 is completely worn so that its diameter is reduced to c, a new large diameter grinding wheel a, must be substituted for the worn wheel. With the large diameter grinding wheel rejecting pin 21 positioned at location 21', it is impossible to mount a large diameter wheel upon the spindle 2. If an attempt is made to shift the pin 21 to its position at 8a in the arcuate slot 8, it is first necessary to replace the high-speed large diameter pulley 19 with the lowspeed small diameter pulley 18 since the rejecting means 20a abuts the large diameter pulley 19 to prevent swinging motion of the linkage away from the axis of the spindle 2. Accordingly, when the high-speed large diameter pulley 19 is removed and the low-speed small diameter pulley 18 substituted therefor, the rejecting means 20a is free to move away from the axis of the spindle 2 which enables the pin 21 to move to its first position which position is furthest removed from the grinding wheel and its axis of rotation. With the grinding wheel rejecting pin 21 away from the grinding wheel 3, the pin does not obstruct replacement of the worn wheel c with a new large diameter wheel a.

The present invention eliminates at least one significant safety hazard. Without such an arrangement it is possible to mount a new large diameter grinding wheel upon the spindle while the transmission between the motor 9 and the spindle 2 is such that the peripheral speed of the large diameter wheel will be excessive. Under these operating conditions the excessive peripheral speed of the grinding wheel can easily destroy the machinery and shatter the grinding wheel. On the other hand, with the present arrangement it is impossible to mount a new large diameter grinding wheel when the high-speed large diameter pulley 19 is connected to drive the grinding wheel.

What is claimed is:

1. An apparatus for preventing circumferential overspeedwheel comprising a spindle with a grinding el conne thereto, motivating means connected to the spindle for rotating the grinding wheel, the motivating means including a small diameter pulley for rotating a large diameter wheel and a large diameter pulley for rotating a worn substantially less than large diameter grinding wheel, and a movable linkage connected between the periphery of the grinding wheel and the periphery of the motor pulley connected to rotate the grinding wheel, the movable linkage having a first position in which it is located directly adjacent the periphery of the small diameter pulley and also directly adjacent the periphery of a large diameter grinding wheel, and a second position in which it is located directly adjacent the periphery of the large diameter pulley and also directly adjacent the periphery of a worn substantially less than large diameter grinding wheel, the second position of the linkage preventing replacement of a completely worn grinding wheel with a new large diameter grinding wheel until the linkage is shifted to the first position, and the large diameter pulley preventing shifting of the linkage to the first position until the large diameter pulley is replaced with the small diameter pulley whereby a new large diameter grinding wheel may only be positioned on the spindle after the large diameter pulley is removed thereby preventing circumferential overspeeding of a new large diameter grinding wheel.

2. An apparatus as in claim 1 wherein the linkage includes a pin at the end thereof located directly adjacent the periphery of the grinding wheel, and a stationary wheel guard substantially surrounding the grinding wheel with an arcuate slot therein for receiving the pin, one end of the slot being closer to the axis of rotation of the grinding wheel than the other end of the slot and the pin being located in the slot at the end thereof which is closer to the axis of rotation of the grinding wheel when the linkage is located in the second position.

3. An apparatus as in claim 2 wherein the linkage is pivotally connected for swinging movement between the first and second positions. 

1. An apparatus for preventing circumferential overspeeding of a grinding wheel comprising a spindle with a grinding wheel connected thereto, motivating means connected to the spindle for rotating the grinding wheel, the motivating means including a small diameter pulley for rotating a large diameter grinding wheel and a large diameter pulley for rotating a worn substantially less than large diameter grinding wheel, and a movable linkage connected between the periphery of the grinding wheel and the periphery of the motor pulley connected to rotate the grinding wheel, the movable linkage having a first position in which it is located directly adjacent the periphery of the small diameter pulley and also directly adjacent the periphery of a large diameter grinding wheel, and a second position in which it is located directly adjacent the periphery of the large diameter pulley and also directly adjacent the periphery of a worn substantially less than large diameter grinding wheel, the second position of the linkage preventing replacement of a completely worn grinding wheel with a new large diameter grinding wheel until the linkage is shifted to the first position, and the large diameter pulley preventing shifting of the linkage to the first position until the large diameter pulley is replaced with the small diameter pulley whereby a new large diameter grinding wheel may only be positioned on the spindle after the large diameter pulley is removed thereby preventing circumferential overspeeding of a new large diameter grinding wheel.
 2. An apparatus as in claim 1 wherein the linkage includes a pin at the end thereof located directly adjacent the periphery of the grinding wheel, and a stationary wheel guard substantially surrounding the grinding wheel with an arcuate slot therein for receiving the pin, one end of the slot being closer to the axis of rotation of the grinding wheel than the other end of the slot and the pin being located in the slot at the end thereof which is closer to the axis of rotation of the grinding wheel when the linkage is located in the second position.
 3. An apparatus as in claim 2 wherein the linkage is pivotally connected for swinging movement between the first and second positions. 